The present invention relates to a system for controlling the pitch of the blades of a propeller of a turbomachine, and to a turbomachine having propeller(s) for an aircraft fitted with such a system for controlling the pitch of the propeller.
More particularly, although not exclusively, the turbomachine can be either a turboprop having one or more propulsive propellers, or a turbo-engine equipped with contra-rotating propulsive propellers, and termed “open rotor” or “unducted fan”, wherein the system for controlling the pitch of the blades of the invention can adapt regardless to the propeller or to each propeller of a turboprop or of an open rotor turbo-engine.
Each propeller conventionally comprises a rotating hub with an outer collar or ring having, in the sidewall thereof, cylindrical radial housings distributed regularly and in which the pivot shafts of the blades are received.
In order to allow optimum operation of the turbo-engine depending on the various flight phases encountered, the blades of the propeller can rotate via the intermediary of their pivot shafts or pivots in the radial housings of the hub, substantially radially (aligned parallel or not) with respect to the axis of rotation of the hub. To that end, they are simultaneously driven (an angular offset can exist from one blade to another) in rotation with respect to the housings of the hub, by means of an appropriate control system by means of which the setting of the blades of the propeller, that is to say their pitch, can be adjusted in flight.
This system for controlling the pitch of the blades covers, for example in the case of a turbo-engine having twin propellers, an angular range of rotation between two end positions, specifically a “reverse” end position in which the blades extend, for example by 30°, beyond the plane which is transverse (or longitudinal) with respect to the axis of the turbo-engine (the forward direction of the airplane) in order to help brake the aircraft, in the manner of conventional thrust reversers, and a “feathered” end position in which the blades are then effaced as much as possible with respect to the forward direction of the airplane, for example in the event of engine shutdown, and thus present the least resistance (drag) possible. The angular range of the blades between the feathered and reverse positions is for example of the order of approximately 120°.